One kind of cylinder lock includes a locking member, a set of locking discs arranged in succession, and intermediate discs sseparating the locking discs from each other. Each locking disc is provided both with a peripheral notch and with a key opening that is bounded by a key-engaging surface of the disc. The key openings jointly form a keyway into which a key for the lock can be inserted, and the locking discs are turnable by engagement of combination surfaces of the key with the key-engaging surfaces of the locking discs to a position in which the peripheral notches are arranged in line forming a channel into which the locking member is able to move so that the whole set of discs is released from locking engagement of the locking member and is able to turn, allowing force transmission from the key in a desired manner.
The key has a blade or shank, and in the context of this type of lock the pitch of a key is the mutual positioning of the combination surfaces in the axial direction of the key blade. With regard to preventing picking of the lock it is important that the pitch of the key cannot, at least not easily, be directly detected through the key way from the lock cylinder. On the other hand by changing the pitch of the key the number of different opening variations available can naturally be increased remarkably.
One way of changing the pitch of a key is to use locking discs and intermediate discs of different thickness in the same set of discs of the lock, whereby the pitch of the key can be changed by changing the mutual positions of discs of different thickness in the set of discs. A disadvantage of this solution is the necessity of making discs of different thickness which increases the number of items to be stored. Additionally, using discs of different thickness in the same filling of a cylinder lock is inconvenient with regard to automation of the assembling procedure.
An object of the invention is to provide a simple solution for alteration of the pitch of the key of the lock so that the number of opening variations can be increased and, at the same time, picking of the lock can be made more difficult. A further object is to make the solution favorable with regard to production technology and to avoid making the construction of the lock more complicated.